Download Guidebook as .pdf (29.1 Mb) - Carolina Geological Society
Download Guidebook as .pdf (29.1 Mb) - Carolina Geological Society Download Guidebook as .pdf (29.1 Mb) - Carolina Geological Society
GEOLOGY OF THE WESTERN PART OF THE CAROLINA TERRANE IN NORTHWESTERN SOUTH CAROLINA Fig. 7. View northwest across Stop 4, Neal Shoals and metagabbro in granite and diorite. Various granitoid rocks make up the majority of the exposure. At least two types of mafic dikes and numerous pegmatite dikes crosscut the older units. Some rocks have a well developed tectonic foliation, but others are essentially undeformed. Where foliation and layering are developed they typically strike northnortheast and dip steeply east-southeast, approximately parallel to the regional trend. The outcrops here show many features typical of the Charlotte belt intrusive complexes in this region, but elsewhere they are mostly exposed piecemeal in small saprolitic outcrops. Here they are well displayed in one small area. For convenience in pointing out the features, the exposure is divided into three parts, northern, central and southern, but they are all interpreted to be aspects of a single intrusive complex. The northern part (Fig. 7) is mostly foliated biotite granite with numerous inclusions of mafic rocks, all of which are cut by pegmatite dikes. The mafic inclusions are mostly amphibolite and hornblende gneiss that are typically elongate and oriented parallel to the regional trend. Some inclusions have wispy and stringy ends, suggesting partial assimilation and mixing with the granite magma. The central part (Fig. 7) of the outcrop is mostly a variety of mafic rocks with some granite, cut by a mafic dike and numerous pegmatite dikes. The largest mafic body is a finegrained biotite amphibolite with porphyroblasts of hornblende and relict (?) phenocrysts of plagioclase. The mafic dike is about one meter thick and has strong ductile deformation along its contacts. Rotation of the foliation and layering in the adjacent granite and amphibolite indicate that the block north of the dike moved relatively eastward. The dike is a metagabbro, with mineral assemblages indicative of amphibolite facies metamorphism. The southern part of the outcrop is mainly strongly foliated coarse-grained granite, with some mafic inclusions, that is cut by a fine-grained, foliated mafic dike and many pegmatite dikes. In the steep bank on the eastern side of the outcrop, colluvium as much a two meters thick unconformably overlies saprolite of the intrusive complex. The rocks here are interpreted to have been emplaced during a single protracted sequence of magmatic events. The 7
Allen J. Dennis and Others Fig. 8. Geologic map of a portion of the Glenn Springs and Jonesville quadrangles, showing the location of Stops 5, 6, 7. Light grey - mafic metavolcanic rocks; outlined areas within light grey - quartz sericite schist or silicification; no pattern - felsic metavolcanic rocks; dark grey - metapyroxenite-hornblendite; double bar random pattern - metagabbro; rippled gneiss pattern - Mean Crossroads metadiorite-diorite gneiss; random dot pattern - foliated biotite porphyry granodiorite; aligned crosses - undeformed, unmetamorphosed diorite; single bar random pattern - Bald Rock granite. Adapted from Dennis and Wright (1996). 8
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Allen J. Dennis and Others<br />
Fig. 8. Geologic map of a portion of the Glenn Springs and Jonesville quadrangles, showing the location of Stops 5, 6, 7. Light<br />
grey - mafic metavolcanic rocks; outlined are<strong>as</strong> within light grey - quartz sericite schist or silicification; no pattern - felsic<br />
metavolcanic rocks; dark grey - metapyroxenite-hornblendite; double bar random pattern - metagabbro; rippled gneiss pattern -<br />
Mean Crossroads metadiorite-diorite gneiss; random dot pattern - foliated biotite porphyry granodiorite; aligned crosses - undeformed,<br />
unmetamorphosed diorite; single bar random pattern - Bald Rock granite. Adapted from Dennis and Wright (1996).<br />
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